Abstract:

An optical fiber adapted to carry optical power for powering an electrical
device and also optionally adapted to carry optical data for signal
processing. The optical fiber capable of carrying both optical data and
optical power includes a central data waveguide region that carries data
light and an annular power waveguide region concentrically surrounding
the data waveguide region and adapted to carry relatively large amounts
of optical power. A first annular isolation region between the data and
power waveguide regions and that includes microstructures serves to
optically isolate the waveguide regions. An outer annular isolation
region serves to confine power light to the power waveguide region and
contributes to the bend-resistance of the optical fiber. An optical power
and optical data distribution system that utilizes the optical fiber is
also described.

Claims:

1. An optical fiber for optical power transmission, comprising:an annular
power waveguide region adapted to carry power light, said annular power
waveguide region comprising an inner radius of greater than 5 μm, a
width (W3) greater than 5 μm, and a relative refractive index
percent (Δ3(%)) greater than or equal to 1%.

4. The optical fiber of claim 1, wherein said annular power waveguide
region is capable of propagating at least 5 modes at 850 nm.

5. The optical fiber of claim 1, wherein the optical fiber is capable of
carrying an amount of optical power, and wherein the annular power
waveguide region is capable of carrying greater than 90% of the amount of
optical power.

6. The optical fiber of claim 1, wherein no region inside a radius of 5
μm has a relative refractive index percent of greater than 0.5%.

7. An optical fiber for optical power transmission, comprising:an inner
isolation region comprising glass having microstructures formed therein
and having a relative refractive index Δ2, inner and outer
radii r1 and r2 that define an area
A2=r.sub.2.sup.2-ri2, and wherein
-400.ltoreq.Δ2A.sub.2.ltoreq.-20;an annular power waveguide
region surrounding the inner isolation region and adapted to carry power
light;an outer annular isolation region comprising glass having
microstructures formed therein and having a relative refractive index
Δ4, inner and outer radii r4 and r5 that define an
area A4=r.sub.5.sup.2-r.sub.4.sup.2, and wherein
-6000.ltoreq.Δ4A.sub.4.ltoreq.-100; anda cladding surrounding
the outer annular isolation region.

10. The optical fiber of claim 7, wherein the power waveguide region has
an attenuation αp in the range 0.16
dB/km≦αp≦50 dB/km.

11. An optical power distribution system, comprising:the optical fiber of
claim 7 having an input end and an output end;a power light source
optically coupled to the annular power waveguide region at the optical
fiber input end and adapted to generate the power light; anda
photovoltaic power converter optically coupled to the annular waveguide
region at the optical fiber output end and adapted to receive the power
light outputted by the power waveguide region and convert the power light
to an electrical power signal.

12. An optical data and power distribution system, comprising:the optical
fiber of claim 8 having an input end and an output end;a data light
source optically coupled to the data waveguide region at the optical
fiber input end and adapted to generate the data light;a power light
source optically coupled to the annular power waveguide region at the
optical fiber input end and adapted to generate the power light;a
photodetector optically coupled to the data waveguide region at the
optical fiber output end and adapted to detect the data light outputted
by the data waveguide region; anda photovoltaic power converter optically
coupled to the annular waveguide at the optical fiber output end and
adapted to receive the power light outputted by the power waveguide
region and convert the power light to an electrical power signal.

13. The system of claim 12, wherein the data and power light sources are
concentrically arranged to correspond to the associated data and power
waveguide regions.

14. An optical fiber for optical power and optical data transmission,
comprising:a central data waveguide region adapted to carry data light;an
annular power waveguide region concentrically surrounding the central
waveguide region and adapted to carry power light;an inner isolation
region arranged between the central data waveguide region and the annular
power waveguide region and comprising glass having microstructures formed
therein and having a relative refractive index Δ2, inner and
outer radii r1 and r2 that define an area
A2=r.sub.2.sup.2-r.sub.1.sup.2, and wherein
-400.ltoreq.Δ2A.sub.2.ltoreq.-20; andan outer annular
isolation region surrounding the annular power waveguide region and that
serves to confine the power light to the annular power waveguide region.

16. The optical fiber of claim 14, wherein the central data waveguide
region has a relative refractive index Δ1, the annular power
waveguide region has a relative refractive index Δ3, and
wherein the optical fiber satisfies at least one of the following
conditions:a) the central data waveguide region has a central section
with Δ1>0 and an outer section with Δ1=0; andb) the
annular power waveguide region has a central section with
Δ3>0 and surrounding outer sections with Δ3=0.

18. The optical fiber of claim 17, said relative refractive index
(Δ3(%)) is greater than 8%.

19. The optical fiber of claim 14, wherein said annular power waveguide
region is capable of propagating at least 5 modes at 850 nm.

20. The optical fiber of claim 14, wherein the power waveguide region has
an attenuation αp in the range 0.16
dB/km≦αp≦50 dB/km.

21. An optical power and optical data distribution system, comprising:the
optical fiber of claim 14 having an input end and an output end;a data
light source optically coupled to the central data waveguide region at
the optical fiber input end and adapted to generate the data light;a
power light source optically coupled to the annular power waveguide
region at the optical fiber input end and adapted to generate the power
light;a photodetector optically coupled to the central data waveguide
region at the optical fiber output end and adapted to detect the data
light outputted by the central data waveguide region; anda photovoltaic
power converter optically coupled to the annular power waveguide region
at the optical fiber output end and adapted to receive the power light
outputted by the annular waveguide and convert the power light to an
electrical power signal.

22. The system of claim 21, wherein the photodetector and photovoltaic
power converter are concentrically arranged so as to operatively
correspond to the associated central waveguide and annular waveguide.

23. The system of claim 21, wherein the photodetector and the photovoltaic
power converter have respective detection areas, and wherein the
photodetector and photovoltaic power converter are positioned relative to
the optical fiber output end so that the data light and power light
respectively cover substantially the entirety of the respective detection
areas.

24. The system of claim 21, wherein the data and power light sources are
concentrically arranged to be operably associated with the central and
annular waveguides.

25. The system of claim 21, wherein the power light source and/or the data
light source include(s) at least one vertical-cavity surface-emitting
laser (VCSEL).

26. A method of transmitting optical power light in an optical fiber
having an input end and an output end, comprising:inputting the power
light at the input end into an annular power waveguide region defined by
inner and outer isolation regions and having an attenuation αp
in the range 0.16 dB/km≦αp≦50 dB/km;
andoutputting the power light at the output end as an annular power light
beam.

27. The method of claim 26, wherein the inner isolation region is annular
and further including:inputting at the input end data light into a
central data waveguide region immediately surrounded by the inner annular
isolation region so as to be optically isolated from the power waveguide
region; andoutputting the data light at the output end as a central data
light beam concentrically surrounded by the annular power light beam.

28. The method of claim 26, wherein at least one of the inner and outer
isolation regions includes at least one of: non-periodically disposed
holes, photonic crystals and fluorine dopants.

29. The method of claim 26, wherein the annular power light beam has an
output optical power of at least 1 W.

30. A method of transmitting data light and optical power light in an
optical fiber having an input end and an output end, comprising:a) at the
input end:inputting the data light into a central data waveguide
region;inputting the power light into an annular power waveguide region
surrounding the central data waveguide region and optically isolated
therefrom;b) at the output end:outputting the data light at the output
end as a central data light beam; andoutputting the power light at the
output end as an annular power light beam that surrounds the central data
light beam.

31. The method of claim 30, further including:converting the data light to
an electrical data signal and providing the electrical data signal to a
signal processor; andconverting the power light to an electrical power
signal and providing the electrical power signal to at least one
electrical device so as to power the at least one electrical device.

32. The method of claim 30, wherein converting the data light into an
electrical data signal and converting the power light to electrical power
signal further includes detecting the data light and power light with a
photodetector and a photovoltaic power converter concentrically arranged
so as to be operably associated with the central and annular waveguides.

33. The method of claim 30, further including generating the data light
and power light using a concentric arrangement of a central data light
source and an annular power light source that are respectively optically
coupled to the central data waveguide region and the annular power
waveguide region.

34. The method of claim 30, including substantially optically isolating
the data waveguide region and the annular power waveguide region by
providing therebetween an annular isolation region that includes at least
one of: photonic crystals, non-periodically disposed holes, periodically
disposed holes, and fluorine dopants.

Description:

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001]This application claims the benefit of, and priority of U.S.
Provisional Patent Application No. 60/927,977 filed on May 7, 2007, the
content of which is relied upon and incorporated herein by reference in
its entirety.

BACKGROUND OF THE INVENTION

[0002]1. Field of the Invention

[0003]The present invention relates generally to optical fibers, and in
particular to an optical fiber capable of transmitting optical power or
both optical power and optical data.

[0004]2. Technical Background

[0005]Powering electrical devices (including electronic devices) using
copper wires is problematic in certain environments where electrical
isolation is required. For example, in high-voltage power distribution
lines, the copper wire connecting the ground station to the
current-sensing system located at the top of the high-voltage line
requires a complex, bulky and heavy isolation system, which is eliminated
if the sensor is driven using a fiber system.

[0006]Due to its dielectric properties, a fiber optic system is
intrinsically insensitive to electric and electromagnetic interference.
Accordingly, one alternative to using copper wires to power electrical
devices is to use optical fibers instead. An optical-fiber-based power
delivery system uses high optical power emitted from a laser source. The
laser light is inputted at an input end of the optical fiber, transmitted
through the length of the optical fiber, and is converted into electrical
power at the output end of the optical fiber. The electrical power is
then used to drive one or more electrical devices located at or near the
output end of the optical fiber.

[0007]Present-day optical-fiber-based power delivery systems use standard
telecommunication optical fibers. It would be desirable to have
alternative and improved fiber designs for power delivery.

SUMMARY OF THE INVENTION

[0008]An aspect of the invention is an optical fiber for optical power
transmission. The optical fiber includes an annular power waveguide
region adapted to carry power light. The annular power waveguide region
has an inner radius of greater than 5 μm, a width greater than 5
μm, and a relative refractive index percent of greater than 1%. Other
embodiments of the optical fiber have relative refractive index
percentages of greater than 3% and greater than 8%.

[0009]Another aspect of the invention is an optical fiber for optical
power transmission. The optical fiber includes an inner isolation region
comprising glass having microstructures formed therein and having a
relative refractive index Δ2, inner and outer radii r1
and r2 that define an area A2=r22-r12, and
wherein -400≦Δ2A2≦-20. The optical fiber
also has an annular power waveguide region surrounding the inner
isolation region and adapted to carry power light. The optical fiber
further includes an outer annular isolation region comprising glass
having microstructures formed therein and having a relative refractive
index Δ4, inner and outer radii r4 and r5 that
define an area A4=r52-r42, and wherein
-6000≦Δ4A4≦-100. The optical fiber also
includes a cladding surrounding the outer annular isolation region.

[0010]Another aspect of the invention is an optical power distribution
system that uses the optical fiber of the present invention. The system
includes a power light source optically coupled to the annular power
waveguide region at the optical fiber input end and adapted to generate
the power light. The system also includes a photovoltaic power converter
optically coupled to the annular waveguide region at the optical fiber
output end and adapted to receive the power light outputted by the power
waveguide region and convert the power light to an electrical power
signal.

[0011]Another aspect of the invention is a power/data (P/D) optical fiber
for optical power and optical data transmission. The optical fiber
includes a central data waveguide region adapted to carry data light and
an annular power waveguide region concentrically surrounding the central
waveguide region and adapted to carry power light. The optical fiber
includes an inner isolation region arranged between the central data
waveguide region and power waveguide region and that comprises glass
having microstructures formed therein and having a relative refractive
index Δ2, inner and outer radii r1 and r2 that
define an area A2=r22-r12, and wherein
-400≦Δ2A2≦-20. The optical fiber also
includes an outer annular isolation region surrounding the annular power
waveguide region and that serves to confine the power light to the
annular power waveguide region.

[0012]Another aspect of the invention is an optical data and power
distribution system that uses the P/D optical fiber of the present
invention. The system includes a data light source optically coupled to
the data waveguide region at the optical fiber input end and adapted to
generate the data light, and a power light source optically coupled to
the annular power waveguide region at the optical fiber input end and
adapted to generate the power light. The system also includes a
photodetector optically coupled to the data waveguide region at the
optical fiber output end and adapted to detect the data light outputted
by the data waveguide region. The system also includes a photovoltaic
power converter optically coupled to the annular waveguide at the optical
fiber output end and adapted to receive the power light outputted by the
power waveguide region and convert the power light to an electrical power
signal.

[0013]Another aspect of the invention is a method of transmitting optical
power light in the optical fiber according to the present invention. The
optical fiber has an input end and an output end. The method includes
inputting the power light at the input end into an annular power
waveguide region defined by inner and outer isolation regions and having
an attenuation αp in the range 0.16
dB/km≦αp≦50 dB/km. The method also includes
outputting the power light at the output end as an annular power light
beam.

[0014]Another aspect of the invention is a method of transmitting data
light and optical power light in the P/D optical fiber according to the
present invention, wherein the P/D fiber has an input end and an output
end. The method includes, at the input end, inputting the data light into
a central data waveguide region and inputting the power light into an
annular power waveguide region surrounding the central data waveguide
region and optically isolated therefrom. The method also includes, at the
output end, outputting the data light at the output end as a central data
light beam, and outputting the power light at the output end as an
annular power light beam that surrounds the central data light beam.

[0015]The optical fibers disclosed herein have a number of advantages over
the prior art fibers. For example, the optical fibers of the present
invention are designed to carry power at relatively high optical power
levels (e.g., greater than 100 W) and so are less prone to light-induced
damage. Such fibers are also capable of avoiding damage even when bent
into relatively small radii, which is not uncommon when such fibers are
deployed in the field. Also, the refractive index profiles of the fibers
disclosed herein may optionally be formed without having to resort to
using dopants other than airlines dispersed in a glass comprised of
silica that add to the attenuation of the fiber, thereby reducing the
optical power transmission efficiency. Further, unlike standard
telecommunication optical fibers that transmit most of the power in a
centrally located waveguide region, the fibers disclosed herein are
designed so that the power is transmitted in an annular power waveguide
region. The ring-shaped mode associated with the annular power waveguide
region corresponds to the most sensitive receiving area of the type of
photovoltaic cells used in optical power delivery systems. This allows
for improved conversion efficiency i.e., for the same input optical
power, more output electrical power is obtained. Further, regular optical
fibers have a mode with high intensity in the center, which causes
heating of the center of the photovoltaic detector, which in terms limits
performance of the optical power delivery system.

[0016]Moreover, many electrical devices that utilize electrical power
converted from optical power are designed to process and transmit data.
As explained below, the fibers disclosed herein include embodiment that
carry both high optical power and optical data signals, with the optical
power and the optical data signals carried in separate portions of the
same optical fiber. This approach reduces cost and simplifies the power
delivery system.

[0017]Additional features and advantages of the invention will be set
forth in the detailed description which follows, and in part will be
readily apparent to those skilled in the art from that description or
recognized by practicing the invention as described herein, including the
detailed description which follows, the claims, as well as the appended
drawings.

[0018]It is to be understood that both the foregoing general description
and the following detailed description present embodiments of the
invention, and are intended to provide an overview or framework for
understanding the nature and character of the invention as it is claimed.
The accompanying drawings are included to provide a further understanding
of the invention, and are incorporated into and constitute a part of this
specification. The drawings illustrate various embodiments of the
invention, and together with the description, serve to explain the
principles and operations of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

[0019]FIG. 1 is a schematic side view of a section of optical fiber
according to the present invention;

[0020]FIG. 2 is a cross-sectional view of the optical fiber of FIG. 1 as
taken along the line 2-2 in FIG. 1, illustrating the different regions of
an example embodiment of a P/D optical fiber that allows the optical
fiber to transmit both optical power and optical data;

[0021]FIG. 3 is a plot of an idealized relative refractive index profile
Δ(%) as a function of optical fiber radius r associated with the
example embodiment of the P/D optical fiber as illustrated in the
cross-sectional diagram of FIG. 2;

[0022]FIG. 4 is a plot similar to that of FIG. 3 illustrating an example
embodiment of the optical fiber of the present invention that carries
optical power but not optical data;

[0023]FIG. 5 is a cross-sectional schematic diagram similar to FIG. 2
illustrating the different regions of the optical fiber associated with
the refractive index profile of FIG. 4;

[0024]FIG. 6 is a schematic diagram of an example embodiment of an optical
power and optical data distribution system according to the present
invention that uses the P/D optical fiber of the present invention;

[0025]FIG. 7 is a schematic plan view of an example embodiment of a
VCSEL-based light source unit that facilitates optical coupling of power
light into the annular power waveguide region and data light into the
central data waveguide region;

[0026]FIG. 8 is a schematic diagram of the various optical fiber sections
superimposed on the light source unit of FIG. 7, illustrating a preferred
correspondence between the light-emitting elements and the data and power
waveguide sections;

[0027]FIG. 9 is a schematic front-on view of an example embodiment of a
detector unit of the O/E converter unit of the optical power and optical
data distribution system of FIG. 6, wherein the photodetector and
photovoltaic power converter are concentrically arranged; and

[0028]FIG. 10 is a schematic perspective diagram of an example embodiment
of the detector unit of FIG. 9 shown operatively arranged relative to the
output end of the P/D optical fiber of the present invention so that the
data light beam and the power light beam are respectively incident upon
the entirety of the detection areas of the photodetector and the
photovoltaic power converter.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0029]Reference will now be made in detail to the present preferred
embodiments of the invention, examples of which are illustrated in the
accompanying drawings. Whenever possible, the same reference numbers and
symbols are used throughout the drawings to refer to the same or like
parts.

[0030]In the discussion below, the "refractive index profile" is the
relationship between refractive index or relative refractive index and
waveguide fiber radius. The "relative refractive index percent"is defined
as Δ(%)=[(ni2-nc2)/2ni2]×100,
where ni is the maximum refractive index in region i, unless
otherwise specified, and nc is the average refractive index of the
cladding region, as discussed below. As used herein, the relative
refractive index percent is represented by Δ(%) and its values are
given in units of "%", unless otherwise specified or as is apparent by
the context of the discussion. As used herein, "Δ(%)" refers to
relative refractive index percent at a wavelength of 1550 nm.

[0031]In the various example design conditions for the optical fiber as
specified below, the "relative refractive index"
Δi=[(ni2-nc2)/2ni2] is used
unless otherwise noted.

[0032]In cases where the refractive index of a region is less than the
average refractive index of the cladding region, the relative refractive
index percent is negative and is referred to as having a "depressed
region" or a "depressed index," and is calculated at the point at which
the relative refractive index is most negative unless otherwise
specified. In cases where the refractive index of a region is greater
than the average refractive index of the cladding region, the relative
refractive index percent is positive and the region can be said to be
raised or to have a positive index.

[0033]An "updopant" is herein considered to be a dopant which has a
propensity to raise the refractive index relative to pure undoped
SiO2. A "downdopant" is herein considered to be a dopant which has a
propensity to lower the refractive index relative to pure undoped
SiO2. An updopant may be present in a region of an optical fiber
having a negative relative refractive index when accompanied by one or
more other dopants which are not updopants. Likewise, one or more other
dopants which are not updopants may be present in a region of an optical
fiber having a positive relative refractive index. A downdopant may be
present in a region of an optical fiber having a positive relative
refractive index when accompanied by one or more other dopants which are
not downdopants. Likewise, one or more other dopants which are not
downdopants may be present in a region of an optical fiber having a
negative relative refractive index.

[0034]In many of the examples described herein employ a 125 micron
diameter optical fiber (unless otherwise stated) because of the
preference to comply with the majority standards used in the
telecommunication industry. However, the inventive fibers disclosed
herein are equally applicable for thinner fiber diameter applications
such as less than 100 micron (and even less than 85 micron) diameter
applications (e.g., 80 micron diameter fiber is used for fiber optic
gyroscopes). With power over fiber applications, industry standards have
not yet been decided and implemented and therefore one could also use
larger diameter fibers (greater than 150 micron, e.g., 200-500 micron
diameter) to carry more power per area. Examples of larger diameter
fibers are shown below.

[0035]Other techniques to form depressed index regions besides the use of
downdopants, such through the use of microstructures, are used in example
embodiments of the present invention and are described in greater detail
below. Microstructures include, for example, non-periodic and period
microvoids or nanostructured features, such as photonic crystals.

[0036]The "effective area" is defined as:

Aeff=2π(∫f2 r dr)2/(∫f4 r dr),

where the integration limits are 0 to ∞, and f is the transverse
component of the electric field associated with light propagated in the
waveguide. As used herein, "effective area" or "Aeff" refers to
optical effective area at a wavelength of 1550 nm unless otherwise noted.

[0038]The bend resistance of a waveguide fiber can be gauged by induced
attenuation under prescribed test conditions, for example by wrapping one
or more turns around a cylindrical mandrel having a constant diameter.

[0039]The "volume" of a circular cross-section region is defined by its
relative refractive index multiplied its "area," wherein the "area" is
defined by the square of its radius. Likewise, the volume of an annular
cross-section region is defined by its relative refractive index
multiplied by its area as defined by (ro2-ri2), where
ro is the outer radius and ri is the inner radius.

[0040]In the discussion below, "watts" is abbreviated as "W" and
"milliwatts" as "mW".

P/D Optical Fiber

[0041]FIG. 1 is a schematic side view of an optical fiber 10 according to
the present invention. FIG. 2 is a cross-sectional view of an example
embodiment of optical fiber 10 as taken along the line 2-2 in FIG. 1 and
that is adapted to transmit both optical power and optical data. Such an
optical fiber is referred to herein as a "power/data optical fiber," or
"P/D optical fiber" for short. FIG. 2 illustrates a generalized structure
(i.e., refractive index profile) of P/D optical fiber 10 that enables the
P/D optical fiber to carry both optical power and optical data in
separate waveguide regions. Example embodiments wherein optical fiber 10
includes only a power-carrying waveguide region are discussed below.
Optical fiber 10 is described immediately in connection with the P/D
optical fiber example embodiment for the sake of discussion.

[0042]In an example embodiment, P/D optical fiber 10 has an input end 12,
an output end 14, and a number of different regions or segments-namely, a
central core region 20 of refractive index n1(r) and an outer radius
r1 surrounded by a first annular core region 30 having a refractive
index n2, an inner radius r1 and an outer radius r2, which
in turn is surrounded by second annular core region 40 having a
refractive index n3(r), an inner radius r2 and an outer radius
r3. P/D optical fiber 10 also includes a third annular core region
50 having a refractive index n4, an inner radius r3 and an
outer radius r4.

[0043]In an example embodiment, central core region 20 is comprised of
silica doped with germanium, i.e. germania doped silica, and annular
region 40 consists of pure silica. Dopants other than germanium, singly
or in combination, may be employed within central core region 20, and
particularly at or near the centerline of the optical fiber disclosed
herein to obtain the desired relative refractive index profiles as
discussed below. In preferred embodiments of present invention, central
core region 20 and second annular region 40 have a non-negative
refractive index profiles, while annular regions 30 and 50 have negative
refractive index profiles. In an example embodiment, central core region
20 and annular core region 40 have positive refractive index profiles.

[0044]In some preferred embodiments, P/D optical fiber 10 contains no
index-decreasing dopants. In other preferred embodiments, P/D optical
fiber 10 contains both one or more index-increasing dopants and one or
more index-decreasing dopants.

[0045]With continuing reference to FIG. 2, annular region 50 is surrounded
by an annular cladding region ("cladding") 60 having a refractive index
nc, an inner radius r4 and an outer radius r5. In an
example embodiment, cladding 60 contains no germania or fluorine dopants
therein. In an example embodiment, cladding 60 is pure or substantially
pure silica. In another example of embodiment, cladding 60 contains
fluorine dopant. Cladding 60 may be comprised of a cladding material
which was deposited, for example during a laydown process, or which was
provided in the form of a jacketing, such as a tube in a rod-in-tube
optical preform arrangement, or a combination of deposited material and a
jacket. Cladding 60 may include one or more dopants. In an example
embodiment, cladding 60 is immediately surrounded by a coating 70 that
includes a primary coating P and a secondary coating S that immediately
surrounds the primary coating.

[0046]The refractive index nc of cladding 60 is used to calculate the
relative refractive index percent Δ(%). Since cladding 60 has a
refractive index nc, the relative refractive index percent of the
cladding at a cladding radius rc (where rc>r4) is given
by Δ(rc)=Δ5 (%)=0%. In an example embodiment,
cladding 60 is immediately surrounded by coating 70.

[0047]In the example embodiment illustrated in FIG. 2 and FIG. 3, P/D
optical fiber 10 thus includes two concentrically arranged waveguide
regions: central core region 20 that is suited as a data channel for
carrying relatively low-power optical data signals (e.g., on the order of
10 mW or less, and more typically on the order of 1 mW or less) and
annular region 40 suited as a power channel for carrying relatively high
optical power (e.g., on the order of 10W or more, and typically greater
than a few hundred mW and up to about 100 W or even 1000 Watts)
sufficient to power electrical and/or electronic devices that are remote
from the source of optical power. Accordingly, in the description
hereinbelow, central core region 20 is referred to as the "data waveguide
region" and annular region 40 is referred to as the "power waveguide
region."

[0048]In an example embodiment, annular section 30 has a negative relative
refractive index that serves to substantially optically isolate data
waveguide region 20 and power waveguide region 40 so that data light
carried in the data waveguide region and power light carried in the power
waveguide region do not substantially interact. Generally, "optically
isolated" means that at most only an insubstantial amount of light
("power light") carried in annular power waveguide region 40 is present
in data waveguide region 20. By way of an example described in greater
detail below, in an application where light ("data light") carried in
data waveguide region 20 is detected by a photodetector, it is
undesirable for power light to be present in the data waveguide region in
amounts that can interfere with detecting the data light. Thus, an
"insubstantial" amount of power light in data waveguide region 20 is that
amount of power light that does not significantly interfere with
detecting the data light and the subsequent processing of data carried by
the data light (e.g., does not increase the bit-error rate or
significantly affect the signal-to-noise ratio). In an example
embodiment, an insubstantial amount of power light in data waveguide
region 20 is less than 10% of the power in the data channel wavelength.
Since the amount of light that couples from one waveguide to another is
generally a function of the length and proximity of the two waveguides to
one another, the amount of optical isolation required between data
waveguide region 20 and power waveguide region 40 can be different
depending on the length of optical fiber 10 used. Thus, a 1 km section of
optical fiber 10 will generally require a greater degree of optical
isolation than a 1 m length of optical fiber for a given application.

[0049]Also in an example embodiment, annular section 50 has a negative
relative refractive index present so that it serves to confine power
light to the power waveguide region 40 and thus also serves an isolation
function with respect to cladding 60. Accordingly, annular sections 30
and 50 are respectively referred to hereinbelow as inner and outer
"isolation regions."

[0050]FIG. 3 is a plot of an idealized relative refractive index profile
Δ(%) as a function of optical fiber radius r associated with the
generalized example embodiment of P/D optical fiber 10 according to the
present invention as illustrated in the cross-section of FIG. 2. In an
example embodiment of optical fiber 10, there is no region inside a
radius of 5 μm that has a relative refractive index percent greater
than 0.5%.

[0051]Data waveguide region 20 generally has a relative refractive index
percent Δ(%)≧0, and in the example embodiment of FIG. 3
includes a central sub-section 20A wherein Δ1(%)>0 and an
outer sub-section 20B wherein Δ1(%)=0. Sub-section 20B serves
to further isolate data waveguide region 20 from adjacent inner isolation
region 30 so that more data light is carried within the data waveguide
region rather in the adjacent annular isolation region as an evanescent
wave (field). In an example embodiment for a 125 micron diameter fiber,
the width W1=2r1 of data waveguide region 20 satisfies 3
μm≦W1≦65 μm, which includes the width of typical
single-mode and multi-mode optical telecommunications optical fiber,
i.e., about 3-6 μm for single-mode and 50 to 62.5 μm for multi-mode
both types of which are 125 micron diameter fibers.

[0052]As discussed above, inner and outer isolation regions 30 and 50 each
preferably have negative relative refractive indices Δ2 and
Δ4. In an example embodiment, Δ2=Δ4. In
an example embodiment, inner isolation region 30 and/or outer isolation
region 50 is/are made of glass having microstructures formed therein.
Generally, the more negative the relative refractive index Δ2
of inner isolation region 30, the narrower it can be while still
providing its optical isolation function. In an example embodiment,
Δ2(%)=-1%. Also in an example embodiment, width
W2=r2-r1 of inner isolation region 30 satisfies 20
μm≦W2≦1 μm.

[0053]In example embodiments for a 125 micron diameter fiber, inner
isolation region 30 has an associated area
A2=r22-r12, and in example embodiments satisfies
-400≦Δ2A2≦-20, more preferably satisfies
-200≦Δ2A2≦-20, and most preferably
satisfies -200≦Δ2A2≦-30.

[0054]The width W4=r4-r3 of outer isolation region 50 can
be very large because its size is only limited in practice by the desired
overall diameter of optical fiber 10. In an example embodiment for a 125
micron diameter fiber, W4 satisfies 10
μm≦W4≦50 μm. Like inner isolation region 30, the
more negative the relative refractive index Δ4 of outer
isolation region 50, the narrower it can be while still providing its
optical isolation function. In an example embodiment,
Δ4(%)=-1%. As with inner isolation region 30, outer isolation
region 50 has an associated area A4=r42-r32, and
in an example embodiment satisfies
-6000≦Δ4A4≦-100. A 250 micron diameter
fiber would scale accordingly such that outer isolation region 50 has an
associated area A2=r42-r32, and in one example
embodiment satisfies -12000≦Δ4A4≦-200. That
is, volume, Δ4A4, at a constant width and constant delta
scales with fiber diameter. A four fold volume for 50 would occur with a
500 micron diameter fiber (500/125), that is, in example embodiment
satisfies -24000≦Δ4A4≦-400.

[0056]Power waveguide region 40 generally has a relative refractive index
percent Δ3(%)≧0. In an example embodiment, power
waveguide region 40 has an inner radius r2 of greater than 5 μm,
a width W2=r3-r2 of greater than 5 μm, and a relative
refractive index percent Δ3(%) of greater than or equal to 1%.
In two other example embodiments, power waveguide region 40 has a
relative refractive index Δ3(%) of greater than 3% and of
greater than 8%, respectively. In yet another example embodiment, power
waveguide region 40 is capable of propagating (carrying) at least 5 modes
at 850 nm.

[0057]The example embodiment of optical fiber 10 as illustrated in FIG. 3
shows power waveguide region 40 having a central sub-section 40A wherein
Δ4(%)>0 and outer sub-sections 40B and 40C that surround
the central sub-section wherein Δ4(%)=0. Sub-sections 40B and
40C serve to enhance the isolation of power waveguide region 40 from the
adjacent inner and outer isolation regions 30 and 50 so that more power
light is carried within the power waveguide region rather than in the
adjacent annular isolation regions as an evanescent wave. In an example
embodiment of optical fiber 10 where the optical fiber carries a given
amount of optical power, power waveguide region 40 is capable of carrying
greater than 90% of the total amount of optical power.

[0058]Because optical fiber 10 is adapted to carry large amounts of
optical power (i.e., "high" optical power) in power waveguide region 40,
this waveguide region is provided with a relatively large area so that
the power density (i.e., the intensity I=power/area) is kept below the
light-damage threshold. Accordingly, in an example embodiment for a 125
micron optical fiber, the width W3=r3-r2 of power
waveguide region 40 satisfies 1 μm≦W3≦42.5 μm.
For example, W1 and W4 may be 5 and 10 microns, respectively.
For a 250 micron diameter fiber where the inner and outer isolation
regions, W1 and W4 may be held at 5 and 10 microns,
respectively, the power waveguide region 40 can have an associated width
W3=r3-r2 of power waveguide region 40 larger than that
achieved with a 125 micron diameter fiber and satisfies 42.5
μm≦W3≦110 μm. A 500 micron diameter fiber allows
one to make the ring power waveguide even larger when W1 and W4
held at 5 and 10 microns.

[0059]In an example embodiment, power waveguide region 40 preferably has
an attenuation αp in the range 0.16
dB/km≦αp≦50 dB/km so that as little power light
as possible is lost due to attenuation.

[0060]In a specific example embodiment, power waveguide region 40 has
dimensions corresponding to those of a vertical cavity surface-emitting
laser (VCSEL) light source, as described below in connection with FIG. 8.
Further, power waveguide region 40 preferably has a numerical aperture
(NA) greater than that associated with the VCSEL light source.

Forming the Optical Fiber

[0061]In example embodiments, some or all of the different regions that
make up P/D optical fiber 10 as disclosed herein are made by a vapor
deposition process. Even more preferably, fabrication of some or all of
P/D optical fiber 10 includes using an outside vapor deposition (OVD)
process. Thus, for example, known OVD laydown, consolidation, and draw
techniques may be advantageously used to produce the optical fiber
disclosed herein. Other processes, such as modified chemical vapor
deposition (MCVD) or vapor axial deposition (VAD) or plasma chemical
vapor deposition (PCVD) may be used, either alone or in combination with
any other deposition process. Thus, the refractive indices and the cross
sectional profile of the optical fibers disclosed herein can be
accomplished using manufacturing techniques known to those skilled in the
art including, but in no way limited to, OVD, VAD and MCVD processes.

[0062]Inner and outer isolation regions 30 and 50 need to be sufficiently
deep and/or wide to provide optical isolation between light traveling in
data waveguide region 20 and power waveguide region 40. Further, one or
both of these annular isolation regions are preferably formed in a manner
that increases the bend-resistance of P/D optical fiber 10. As discussed
above, different approaches can be used to form inner and outer isolation
regions 30 and 50, such as via the formation of microstructures (also
called "nanostructured features"), via fluorine doping, or via the
formation of periodic nanostructured features that run the length of the
optical fiber and that are referred to in the art as "photonic crystals."
Example approaches for forming photonic crystals in the inner and/or
outer isolation regions of the present invention are described in U.S.
Pat. Nos. 6,243,522 and 6,445,862, which patents are incorporated by
reference herein.

[0063]Thus, in an example embodiment of P/D optical fiber 10, at least one
of inner and outer isolation regions 30 and 50 comprises glass having
formed therein non-periodically disposed holes (voids) 74. In an example
embodiment, the glass is fluorine-doped while in another example
embodiment the glass is undoped pure silica. By "non-periodically
disposed" or "non-periodic distribution," it is meant that when one takes
a cross-section of the optical fiber (such as shown in FIG. 2), the
non-periodically disposed holes are randomly or non-periodically
distributed across a portion of the fiber. Cross sections similar to FIG.
2 taken at different points along the length of P/D optical fiber 10 will
reveal different cross-sectional hole patterns, i.e., various
cross-sections will have different hole patterns, wherein the
distributions of holes and sizes of holes do not match. That is, the
holes are non-periodic, i.e., they are not periodically disposed within
the fiber structure. These holes are stretched (elongated) along the
length (i.e. in a direction generally parallel to the longitudinal axis)
of the optical fiber (and thus have a longer dimension along the length
of the fiber), but do not extend the entire length of the entire fiber
for typical lengths of transmission fiber. While not wishing to be bound
by theory, it is believed that the holes extend less than a few meters,
and in many cases less than 1 meter along the length of the fiber.

[0064]If non-periodically disposed holes or voids 74 are employed in at
least one of the inner and outer isolation regions 30 and 50, it is
desirable that they be formed such that greater than 95% of and
preferably all of the holes exhibit a mean hole size in the cladding for
the optical fiber which is less than 1550 nm, more preferably less than
775 nm, most preferably less than about 390 nm. Likewise, it is
preferable that the maximum diameter of the holes in the fiber be less
than 7000 nm, more preferably less than 2000 mn, and even more preferably
less than 1550 nm, and most preferably less than 775 nm. In some
embodiments, the fibers disclosed herein have fewer than 5000 holes, in
some embodiments also fewer than 1000 holes, and in other embodiments the
total number of holes is fewer than 500 holes in a given optical fiber
perpendicular cross-section. Of course, the most preferred fibers will
exhibit combinations of these characteristics. Thus, for example, one
particularly preferred embodiment of optical fiber would exhibit fewer
than 200 holes in the optical fiber, the holes having a maximum diameter
less than 1550 nm and a mean diameter less than 775 nm, although useful
and bend resistant optical fibers can be achieved using larger and
greater numbers of holes. The hole number, mean diameter, max diameter,
and total void area percent of holes can all be calculated with the help
of a scanning electron microscope at a magnification of about 800×
and image analysis software, such as ImagePro, which is available from
Media Cybernetics, Inc. of Silver Spring, Md., USA.

[0065]In an example embodiment, holes 74 can contain one or more gases,
such as argon, nitrogen, or oxygen, or the holes can contain a vacuum
with substantially no gas; regardless of the presence or absence of any
gas, the refractive index of the hole-containing region is lowered due to
the presence of the holes. The holes can be randomly or non-periodically
disposed, while in other embodiments the holes are disposed periodically.
In some embodiments, the plurality of holes comprises a plurality of
non-periodically disposed holes and a plurality of periodically disposed
holes. Alternatively, or in addition, as mentioned above the depressed
index can also be provided by downdoping the glass in the hole-containing
region (such as with fluorine) or updoping one or both of the surrounding
regions.

[0066]One or both of inner and outer isolation regions 30 and 50 can be
made by methods that utilize preform consolidation conditions, which are
effective to trap a significant amount of gases in the consolidated glass
blank, thereby causing the formation of voids in the consolidated glass
optical fiber preform. Rather than taking steps to remove these voids,
the resultant preform is used to form an optical fiber with voids, or
holes, therein. As used herein, the diameter of a hole is the longest
line segment whose endpoints are disposed on the silica internal surface
defining the hole when the optical fiber is viewed in perpendicular
cross-section transverse to the optical fiber central axis.

[0068]An example embodiment of optical fiber 10 of the present invention
is similar to the above-described P/D optical fiber but is configured so
that it only delivers optical power and is thus referred to herein as a
"power optical fiber." FIG. 4 is a plot similar to FIG. 3 illustrating an
example embodiment of power optical fiber 10 that does not include data
waveguide region 20. FIG. 5 is a schematic cross-sectional diagram
similar to FIG. 2 illustrating a generalized structure (i.e., refractive
index profile) of power optical fiber 10 according to FIG. 4 that enables
the power optical fiber to carry optical power (power light) in annular
power waveguide region 30. For the sake of consistency, the same
reference numbers and radii are used as for the related embodiments of
P/D optical fiber 10. What was once an inner annular isolation region 30
with an inner radius r1 and outer radius r2 is now simply a
central isolation region with an outer radius r2 (r1''0) that
serves to confine power light to annular power waveguide region 40.

Optical Power and Optical Data Distribution System

[0069]FIG. 6 is an example embodiment of an optical power and optical data
distribution system 200 ("P/D system") according to the present invention
that uses P/D optical fiber 10. P/D system 200 includes a light source
unit 210 that has a power light source 212 adapted to generate light 214
that serves as optical power ("power light") and a data light source 222
adapted to generate light 224 that carries data ("data light"). Light
source unit 210 is optically coupled to input end 12 of P/D optical fiber
10 section in a manner that optically couples data light 224 into data
waveguide region 20 and that optically couples power light 214 into power
waveguide region 40. In an example embodiment, data light source 222 is
operably coupled to a modulation circuit 228 that modulates the data
light so that it carries information.

[0070]P/D system 200 includes an optical-to-electrical (O/E) converter
unit 230 optically coupled to P/D optical fiber output end 14. O/E
converter unit 230 includes a photovoltaic power converter 232 adapted to
receive power light 214 on a light-detecting surface of area A232
(FIG. 9) and convert the received power light into electrical power
signal SP. O/E converter unit 230 also includes a photodetector 242
adapted to receive data light 224 on a light-detecting surface of area
A242 (FIG. 9) and convert the detected data light into an electrical
data signal SD. In an example embodiment, photovoltaic power
converter 232 and photodetector 242 constitute a detector unit 250. O/E
converter unit 230 is electrically connected to at least one electrical
device 252 via an electrical link 254 that carries electrical power
signal SP that powers the at least one electrical device. Likewise,
O/E converter unit 230 is electrically connected to at least one signal
processing unit ("signal processor") 262 via an electrical link 264 that
carries electrical data signal SD to be processed by the at least
one signal processing unit. In an example embodiment, electrical device
252 and signal processor 262 are part of a single electrical unit 270.

[0071]Because power waveguide region 40 is annular and surrounds central
data waveguide region 20, power and data light sources 212 and 222 are
preferably configured to facilitate optical coupling of power light 214
and data light 224 into these respective waveguide regions. FIG. 7 is a
schematic plan view of an example embodiment of light source unit 210
that facilitates such optical coupling. Light source 210 of FIG. 7
includes an array 300 of a number of individual light-emitting elements
302. In an example embodiment, each of light-emitting elements 302 are or
otherwise include VCSELS, with one or more centrally located
light-emitting elements 302D serving to generate data light 224 and one
or more light-emitting elements 302P serving to generate power light 214.

[0072]FIG. 8 is a schematic diagram of the various optical fiber sections
superimposed on light source unit 210 of FIG. 7 to illustrate an example
light source configuration wherein there is correspondence between the
data and power light-emitting elements 302D and 302P and the associated
data and power waveguide regions 20 and 40 of P/D optical fiber 10. FIG.
8 illustrates an example embodiment wherein array 300 of light-emitting
elements is configured to provide optimum optical coupling of power light
214 and data light 224 into the power and data waveguide regions 40 and
20, respectively. In an example embodiment, W1=4 μm, W2=10
μm, W3=33.5 μm, W4=5 μm, and W5=10 μm, which
dimensions yield a total width WT=125 μm. This relatively large
optical fiber width WT makes P/D optical fiber 10 relatively simple
and easy to align to power and data light sources 214 and 224.

[0073]Note also that in the embodiment illustrated in FIG. 8, a width
W3=33.5 μm of power waveguide region 40 corresponds to a mode
area of approximately 6,500 μm2.

[0074]FIG. 9 is a schematic front-on view of an example embodiment of
detector unit 250 of O/E converter unit 230, wherein photodetector 242
and photovoltaic power converter 232 of O/E converter 230 are arranged
concentrically, with the photodetector in the center and the photovoltaic
power converter in the form of an annulus. In an example embodiment, a
central portion of photovoltaic power converter 232 is removed to form an
aperture and photodetector 242 is arranged either within the aperture, or
behind the aperture so that light reaches the photodetector through the
aperture.

[0075]It is generally preferred when detecting light using a detector that
all or substantially all of the detection area be used. FIG. 10 is a
schematic perspective diagram of an example embodiment of detector unit
250 of FIG. 9 shown positioned relative to output end 14 of P/D optical
fiber 10 so that data light 224 and power light 214 are respectively
incident on photodetector 242 and photovoltaic power converter 232 in a
manner that substantially covers the entirety of the associated detection
areas A242 and A232.

[0076]When light source 210 in P/D system 200 is activated, P/D optical
fiber output end 14 outputs from data waveguide region 20 a data light
beam 224B of data light 224 and also outputs from power waveguide region
40 a power light beam 214B of power light 214. Because inner isolation
region 30 separates data waveguide region 20 and power waveguide region
40, there is an annular dark region or "gap" 340 between the
corresponding data and power light beams 224B and 214B. Gap 340 is
advantageous in that it prevents the spillover of power light 214 and
data light 224 between the different detectors. Because of the numerical
apertures NA20 and NA40 associated with data waveguide region
20 and power waveguide region 40, respectively, the corresponding data
and power light beams 224B and 214B diverge. This allows for detector
unit 250 to be larger than the output end 14 of P/D optical fiber 10,
e.g., W25032 2W10, and otherwise sized appropriately to
facilitate receiving the power and data light beams.

[0077]In an example embodiment of the above-described system 200, optical
fiber 10 is the power optical fiber described above in connection with
FIG. 4 and FIG. 5. Because power optical fiber 10 only carries optical
power, light source unit 210 need only include power light-emitting
elements 302P and detector unit 250 only need include photovoltaic power
converter 232.

[0078]It will be apparent to those skilled in the art that various
modifications and variations can be made to the present invention without
departing from the spirit and scope of the invention. Thus it is intended
that the present invention cover the modifications and variations of this
invention provided they come within the scope of the appended claims and
their equivalents.